Patterns of metastatic progression and association with clinical outcomes in canine osteosarcoma: A necropsy study of 83 dogs

Abstract

Osteosarcoma is a highly metastatic primary bone tumour that occurs spontaneously in both pet dogs and humans. Patterns of metastasis to organs beyond the most common site (lung) are poorly characterised and it is unknown whether specific associations between patterns of metastatic progression and patient features exist. This retrospective study characterised the necropsy findings of 83 dogs receiving standardised therapy and clinical monitoring in a prospective clinical trial setting to document patterns of metastasis and correlate outcomes with these patterns and other patient and tumour-specific factors. A total of 20 different sites of metastasis were documented, with lung as the most common site, followed by bone, kidney, liver, and heart. Two distinct clusters of dogs were identified based on patterns of metastasis. There was no significant association between site of enrollment, trial arm, sex, serum alkaline phosphatase (ALP) activity, or tumour location and clinical outcomes. A second cancer type was identified at necropsy in 10 dogs (10/83; 12%). These data showcase the extensive nature of osteosarcoma metastasis beyond the lung and provide a benchmark for clinical monitoring of the disease. Further, this study provides insight into transcriptional features of primary tumours that may relate to a propensity for osteosarcoma metastasis to specific organs and tissues.

Keywords: canine; metastasis; osteosarcoma; transcriptional profiling.

Figure 1:

Representative images of canine osteosarcoma metastases within multiple tissue types (left column) composed of tumor cells with osteoid (right column). (A,B) The lung was the most common location for osteosarcoma metastases. This dog developed multiple osteoid-rich masses. (C-D) Following limb amputation, approximately 40% of dogs developed osteosarcomas in new bone sites. This was the second-most commonly affected location in our study. Other common sites included the (E-F) kidney, liver, and (G-H) heart.

Figure 2.

Cluster analysis of metastasis site data. A. Evolution of Within Cluster sum of squares as a function of number of clusters. Clustering techniques: AGNES (Agglomerative Nested Clustering or bottom-up hierarchical clustering), DIANA (DIvisive ANAlysis clustering or top-down hierarchical clustering), K-means, K-modes B. Heatmap visualizing each cluster. Columns depict metastatic sites, rows depict patients. C. Kaplan-Meier survival plots depicting Overall survival and Disease Free Interval (DFI) of patients belonging to each cluster. P-values were estimated from the log-rank test.

Figure 3:

Hallmark pathway enrichment analysis identifies unique set of pathways upregulated in primary tumors of patients belonging to each cluster.